This study examines how VAW Systems successfully developed a lightweight, compact vent silencer package for a research facility looking to reduce the amount of noise received by residential receptors adjacent to its property.
Project Description
Our client operated a research facility in a mixed land-use area. As part of its testing activities, the research facility operated a noisy, high-pressure relief system which vented to the atmosphere several times per day. The outlet vent for this high-pressure relief was approximately 30 feet above grade; additionally, there were adjacent residential receptors on two sides of the research facility.
The vent could not simply be moved; the high-pressure relief system was complex. At the same time, testing could not simply be halted. A solution that would provide relief for the research facility’s residential neighbors without a dramatic overhaul of the high-pressure relief system was required.
Applied Research
VAW Systems was contracted to research and develop a silencer for this high-pressure relief system. Research started in the field at the research facility. Using acoustic testing devices, we determined the sound power radiation of the relief system under worst-case operating conditions. We then determined how much of this sound would reach the residential receptors. Field testing also allowed us to locate any physical barriers that might hinder our work.
Using specifications sent to us by our client, we began working on a solution at our in-house lab, the VAW Noise Control Applications Laboratory. Using the noise reduction targets we obtained during our in-field testing, we began to design a vent and blow-off silencer to achieve our goals.
Vent and blow-off silencers have three key components: A high-pressure flanged diffuser assembly, an expansion plenum, and a sound-absorbing baffle that abruptly terminates into the atmosphere. Our goal was to create a diffuser that was small and light enough to work within the high-pressure relief system. The size and weight needed to be tightly controlled to minimize the structural support required and address wind loading concerns.
Engineered Solution
Using the parameters we established during field testing and taking advantage of the technologies available to us in the VAW Noise Control Applications Laboratory, we achieved reliable and repeatable results as part of a comprehensive aero-acoustic study.
The silencer package we engineered met the noise criteria we had established; the package was compact and featured a range of diffuser porosities. This design allowed us to achieve an optimal silencer package with relatively low back pressure applied to the stack system. The result? A silencer that met our client’s stringent noise reduction requirements, all while allowing the high-pressure relief system to operate in both optimal and high-stress conditions.
Technical Insights
To achieve a light, compact silencer package, our team focused on optimizing both the diffuser and the sound-absorbing section. The type of openings in the diffuser (small holes or slots), and the orientation of both the diffuser and its openings have an important effect on the dispersion of the system’s impulsive pressure load. By using a variety of openings, we created a range of different diffuser porosities to effectively reduce the sound generated by the system’s impulsive pressure load without needing a larger silencer package.
Challenges and Obstacles
Installing a silencer in a high-pressure relief system presents a number of unique challenges. The goal is to create an unobstructive silencer; pressure must be allowed to pass through the system relatively unencumbered, but the impulsive sound generated by that system must be reduced.
To achieve this goal, thorough testing is required. Testing impulsive noise, which is sudden and sharp, is challenging; specialized measurement equipment and techniques are required. Having worked in noise reduction for decades, VAW Systems has the equipment and knowledge required to accurately test impulsive noise. This allows us to engineer reliable silencer packages that will achieve the desired noise reduction targets.
Additionally, a small, lightweight silencer was needed in order to achieve noise reduction targets without impeding the functioning of the relief system. To do this required careful engineering; our aerodynamic, lightweight design allowed us to create a vent silencer that applied a predictable low back pressure to the stack system.
Conclusion
Our approach involved thorough field testing under both optimal and worst-case conditions, as well as laboratory testing under a variety of conditions to ensure that our silencer would suit our client’s needs. The project was a resounding success; we developed an effective silencer package that did not hinder the operation of the high-pressure relief system.
Vent silencers present a number of design challenges; we overcame these challenges and provided our client with a custom-engineered part that successfully achieved our noise reduction targets. Its residential neighbors no longer have to worry about impulsive noise, and our clients can continue to vent to the atmosphere several times a day without concern for noise ordinance violations.
Our team can design a customized silencer for your business. Whether you’re looking for a vent silencer, blow-off silencer, or a silencer of any other kind, VAW Systems can help.